Grout delivery system for a rock bolt

ABSTRACT

A grout delivery device which includes a body which defines an internal volume ( 18 ), opposing first ( 34 ) and second ( 26 ) apertures in the body, in communication with the volume, through which a rock support tendon ( 50 ) extends, and a grout formation ( 44 ) on the body for connection to a grout source.

BACKGROUND OF THE INVENTION

This invention relates, generally, to the delivery of grout to a rocksupport tendon and more particularly is concerned with a device toassist in delivering grout to a drill hole in which a rock supporttendon is to be anchored.

As used herein “grout” includes a cementitious mixture and any othersettable mixture which can be employed to anchor a rock support tendonin position, and “rock support tendon” includes, without being limited,a rock bolt, a cable anchor and similar support devices.

The grouting of rock support tendons is a widespread practice. The groutprotects the support tendons from any ground water which may be presentand which could cause the support tendons to corrode and, secondly, thesupport performance of the support tendons is enhanced for the groutingincreases the capability of the support tendons to resist shear forcesin the surrounding rock.

When a rock support tendon is grouted in a drill hole, provision must bemade for air which is trapped in the drill hole to escape to atmosphere.One system in use employs a first tube for delivering the grout to thedrill hole and a second tube to allow air to escape from the drill hole.Ends of the tubes protrude into a working place at which the rocksupport tendon is installed and are subject to blast damage—a factorwhich can make grouting difficult or impossible.

In a second approach, of which the applicant is aware, use is made of ahollow spherical device which is seated on an outer side of a bearingplate or washer which is engaged with a protruding end of the rocksupport tendon. Grout is delivered to the drill hole through the hollowinterior of the device. The spherical device is however also exposed tothe workplace and can therefore be damaged by blasting or by movingmachinery.

An object of the present invention is to provide a device whichfacilitates delivery of a grout to a drill hole and which, to asubstantial extent, is protected against damage of the aforementionedkind.

SUMMARY OF INVENTION

The invention provides a grout delivery device which includes a bodywhich defines an internal volume, opposing first and second apertures inthe body, in communication with the volume, through which a rock supporttendon extends, and a grout formation on the body for connection to agrout source.

Preferably the body is at least partly flexible

The body may have a first body portion in which the first aperture islocated and a second body portion in which the second aperture islocated. The second body portion may be movable relative to the firstbody portion at least to a limited extent.

The internal volume may be in the nature of a passage or chamber or asimilar space which is at least partly enclosed.

The flexibility of the body may be achieved in any appropriate way. Forexample different portions of the body may be made from differentmaterials. Another possibility is for the body to be made with one ormore lines of weakness which facilitate flexing of the body. A thirdpossibility is for the body to be formed with formations in the natureof a bellows or the like. These types of construction are exemplary onlyand are non-limiting.

The formation, for connection to the grout source, is preferably locatedon the first body portion.

The first body portion is preferably bulbous.

An outer surface of the first body portion, surrounding the firstaperture, is preferably convex or semi-spherical, conical or the like.Thus a cross-sectional dimension of the first body portion measuredbetween opposing points on the outer surface in a direction which istransverse to an axis of the first aperture, may increase in a directionaway from a mouth of the first aperture.

The second body portion may be substantially tubular. A section of thebody between the first body portion and the second body portion may beslightly flared i.e. of decreasing cross-section from the bulbous firstbody portion to the tubular second body portion.

The formation for connection to the grout source may be in the nature ofa spigot and may include a formation which facilitates engagement of thespigot with an opening, in a member such as a bearing plate, throughwhich the spigot is passed.

The invention also extends to an assembly of a device of theaforementioned kind and a bearing plate which includes a central openingwhich is aligned with the first aperture of the device and a secondopening through which the grout formation of the device passes and,preferably, with which the grout formation is engaged.

A rock support tendon may extend through the first and second aperturesand through the central opening of the bearing plate. A seal may beprovided at an interface of the device and the rock support tendon inthe region of the first aperture. The seal may be of any appropriatekind and, by way of example only, may be constituted by a washer of aflexible material such as rubber which closely surrounds the rocksupport tendon and which engages with an annular gap between the firstbody portion and the tendon. Alternative the body can be formed with asmall collar, which protrudes into the volume, and which closelysurrounds an adjacent surface of the tendon.

The bearing plate could have any suitable shape and, for example, isdomed or flat or semi-conical.

The device may be used in different ways. In one form of the inventionan elongate tube is engaged with the body in direct communication withthe second aperture.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described by way of examples with reference tothe accompanying drawings in which:

FIG. 1 is a side view of a device according to the invention;

FIG. 2 shows the device in perspective;

FIG. 3 is a cross-sectional view, from one side, of the device shown inFIG. 1;

FIG. 4 shows, in cross-section, the device engaged with a rock supporttendon, in one mode of use;

FIG. 5 shows the device used with a rock support tendon in a differentmode of use,

FIG. 6 shows the device when used with a cable anchor; and

FIGS. 7 and 8 are perspective and cross-sectional views respectively ofa device according to a different form of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT

FIGS. 1, 2 and 3 of the accompanying drawings are side, perspective andcross-sectional views respectively of a device 10 used for deliveringgrout to a rock support tendon, according to the invention.

The device includes a body 12 formed by a first body portion 14 and asecond body portion 16.

The body encloses an internal volume 18, in the nature of a chamber.

The first body portion 14 is bulbous and has a convex or semi-sphericalouter surface 20. A first aperture 22 is centrally positioned in theconvex surface.

The second body portion 16 is formed by a short tube 24 which terminatesin a second aperture 26 which directly opposes the first aperture. Anintermediate section 28 between the body portions is flared and reducesin cross-section from the bulbous first body portion to the tubularsecond body portion.

As is evident particularly from FIG. 3 the first body portion 14 has aregion 30 which is formed with ribs which impart to the region abellows-type appearance. As a consequence the region 30 is flexible, atleast to a limited extent, and the first body portion can thus be movedrelative to the second body portion to some extent.

It is desirable for the body to be flexible, at least to a limitedextent, for reasons which are described hereinafter. This flexibilitycan be achieved using any suitable technique and the scope of theinvention is not limited to the use of the bellows-like strucutre. Forexample the body could be made from one or more parts and the region 30or the flared section 28 could be made from a softer and more flexiblematerial than remaining portions of the body. Other approaches toachieve this desired property of flexibility are of course possible e.g.by forming appropriate sections of the body with lines of weakness whichpromote bending or flexing of the body.

In this example of the invention (refer to FIG. 3) an inwardly extendingcollar 34 is positioned at a rim of the first aperture and extends intothe volume 18.

A small spigot 38 is positioned on the outer surface 20. The spigot isto one side of the first aperture and has a frusto-conical leading end40 followed by a small shoulder 42. A passage 44 extends through thespigot.

FIG. 4 illustrates, in cross-section and from one side, one way of usingthe device 10. A rock support tendon 46 has an elongate rigid shank 50which extends through the opposing first and second apertures 22 and 26.A bearing plate 52 is passed onto the shank over the convex outersurface 20 of the bulbous first portion. The bearing plate has a domedcentral area 54 which is sized to fit closely over the convex surface20. The shank extends through a centrally positioned opening 56 in thebearing plate. A shaped washer 58, as is known in the art, is placedover the shank and this is followed by a nut 60 which is threadedlyengaged with a protruding end 62 of the shank.

The bearing plate is formed with a small opening 64 and the spigot 38 ofthe device is passed through this opening. The shoulder 42 abuts andengages with a portion of the outer surface of the bearing plate whichsurrounds the opening.

The shank extends through the tubular second portion 24 into a drillhole 70 formed in a body of rock 74. An outer edge 76 of the bearingplate abuts a surface of a rock face 78 surrounding the drill hole 70.

The device 10 can be used in two ways, at least, depending on the natureof the rock support tendon with which the device is engaged. In one modeof use a tube 80 is engaged with a leading end of the tubular secondportion so that the second aperture 26 is in direct communication withan interior of the tube. The tube can be clamped or otherwise fixed tothe tubular second portion. The tube extends into the hole 70 to arequired extent. Grout from a grout delivery system, not shown, can thenbe injected into the passage 44 in the interior of the spigot. The groutflows into the volume 18 and then passes into an elongate annular volume82 which surrounds the shank and which is bounded by the inner surfaceof the tube. As the grout advances air is expelled from the drill hole,travelling on an outer side of the tube. The air eventually reachesatmosphere through paths which are formed on an outer side of the device10.

In a second mode of use, illustrated in FIG. 5, the shank, designated50A, is formed with an elongate, axially extending, air passage 84. Inthis mode of use the tube 80 is not used. When grout is injected intothe volume 18 it emerges from the second aperture 26 and fills anannular gap 86 between an outer surface of the shank 50A and an opposinginner surface of the drill hole. Air trapped inside the drill hole canescape, as the grout advances, by entering a mouth of the passage 84which is located at a far end of the shank. When grout starts leavingthe passage 84 it is evident to an operator that the drill hole has beencompletely grouted.

In FIGS. 4 and 5 the rock face 78 is generally perpendicular to thelongitudinal direction of the drill hole. This is not necessarily thecase. In many applications, particularly in arduous undergroundconditions, the rock face is inclined to the axial direction of thehole. Clearly, the orientation of the rock support tendon is determinedby the hole direction. Similarly, the orientation of the bearing plateis determined by the orientation of the rock face surrounding the mouthof the drill hole. It is for this reason that a degree of flexibility ofthe body of the device is required. The tubular second portion isinserted into the drill hole and is therefore not able to be moved toany meaningful extent. The bulbous first portion which is captured bythe domed bearing plate must be movable, together with the bearingplate, relatively to the rock support tendon. The bellows-like region 30allows this movement to take place.

FIG. 6 shows the use of the device with a tendon 46A which includes anelongate, slightly flexible, cable 50B, and not a rigid shank.

An end 90 of the cable projects from a mouth of a drill hole 70 formedin a rock body 74, and passes through a volume 18 inside a device 10Awhich is similar to the device 10, but which includes an additionaltubular spigot 98. Other parts of the device 10A, which are the same asparts of the device 10, bear similar reference numbers. The device 10Ais located inside a bearing plate 52 in that it has an opening 100through which the spigot 98 extends.

A breather tube 102 extends through the spigot 98, and the volume 18,into the drill hole 70 and, alongside the cable 50B, to an inner end ofthe drill hole.

A barrel 106 is passed onto the end 90 and a wedge 108 is engaged withthe end 90 and the barrel, which bears against an outer face of thebearing plate 52. These components are used to tension the cable, as isknown in the art. Grout is injected into the drill hole through thespigot 44 and fills the annular space between the cable and a wall ofthe drill hole. Air is expelled through the breather tube 102.

FIGS. 7 and 8 show another device 10B according to the invention inperspective and in cross-section respectively. The device has a body 12Bwith a first, frusto-conical, portion 14B and a second, tubular, portion16B. The portion 14B has a plurality of apertures 112, and twoformations 98B and 44B which correspond to, and which perform the samefunctions as, the spigots 98 and 44 respectively. The apertures 112weaken the body and allow for a degree of relative movement between thebody portions 14B and 16B. A passage 18B, through the body 12B, acts inthe same way as the volume 18.

The device 10B is used in the same way as the device 10A, but preferablywith a bearing plate of a corresponding shape i.e. not as domed as thebearing plate 52.

1. A grout delivery device for use with a bearing plate and a rocksupport tendon which extends through an opening in the bearing plate,the device including a body which defines an internal volume, a firstaperture positioned in a surface of the body which opposes an innersurface of the bearing plate, a second aperture in the body whichopposes the first aperture, the rock support tendon extending throughthe first and second apertures which are in communication with thevolume, and a grout opening in the body which is displaced from thefirst and second apertures and through which grout is injectable intothe volume.
 2. A device according to claim 1 wherein the body includes afirst body, portion in which the first aperture and the grout openingare located and a second body portion in which the second aperture islocated.
 3. A device according to claim 2 wherein the second bodyportion is movable relative to the first body portion at least to alimited extent.
 4. A device according to claim 3 wherein the bodyincludes bellows-type formations which allow the second body portion tobe movable relative to the first body portion.
 5. A device according toclaim 2, wherein an outer surface of the first body portion surroundsthe first aperture and is convex, semi-spherical or conical in shape. 6.A device according to claim 2 wherein the second body portion issubstantially tubular.
 7. A device according to claim 1 wherein thegrout opening is formed by a spigot which projects from the body andthrough which is formed a passage.
 8. An assembly of a device accordingto claim 1 and a bearing plate which includes an opening which isaligned with the first aperture in the body and a second opening whichis in register with the grout opening in the body.
 9. An assemblyaccording to claim 8 which includes a rock support tendon which extendsthrough the first and second apertures and through the opening of thebearing plate.
 10. An assembly according to claim 9 which includes aseal at an interface of the device and the rock support tendon in theregion of the first aperture.
 11. An assembly according to claim 8 whichincludes an elongate tube which is engaged with the body in directcommunication with the second aperture.
 12. An assembly according toclaim 8 wherein the bearing plate has a domed area in which the openingis located.